The presently disclosed embodiments pertain to a novel imaging member, namely, an electrostatic latent image generating member that can generate an electrostatic latent image digitally through a single step charging process. The embodiments provide a novel way of generating an electrostatic latent image without the shortfalls suffered by current photoreceptors, such as for example, charge mobility issues, unstable cycling, surface wear, lateral charge migration and sensitivity to light shock.
In conventional electrophotographic printing, the charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as toner. Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced or printed. The toner image may then be transferred to a substrate or support member (e.g., paper) directly or through the use of an intermediate transfer member, and the image affixed thereto to form a permanent record of the image to be reproduced or printed. Subsequent to development, excess toner left on the charge retentive surface is cleaned from the surface. The process is useful for light lens copying from an original or printing electronically generated or stored originals such as with a raster output scanner (ROS), where a charged surface may be imagewise discharged in a variety of ways.
Thus, it can be seen that current xerographic printing involves multiple steps, such as, charging the photoreceptor; developing the latent images, transferring and fusing the developed images; and, erasing and cleaning the photoreceptor. These multiple steps require many electromechanical components, which leads to more opportunities for system breakdowns or failures. Future trends in the industry are focusing on using machines that are smaller, faster, smarter, less costly and environmentally friendly. Thus, there is a need to re-design engine architecture to achieve machines that use fewer steps and fewer individual components such as for example, a printing apparatus that can create the latent image in a single step during charging, whereby the ROS is no longer needed.
The present embodiments provide an imaging member that allows for the latent image to be created during the charging process. The electrostatic imaging member comprises digitally addressable metallic pads arranged as pixels, sandwiched between a thin-film transistor (TFT) backplane and a thin dielectric surface layer, where each pixel pad can individually be selectively isolated or connected to ground through the transistor backplane. A latent electrostatic image can be created on the dielectric surface of the imaging member by selectively grounding the pixel pads in an imagewise fashion while exposing the dielectric surface of the device to a corona source, such as a corotron. The ionized corona gas will be selectively electrostatically attracted to the grounded pixels under the dielectric layer.
An additional benefit provided by the present embodiments is that the layer on the outer surface of the imaging member can be selected from a range of dielectric materials so as to minimize wear relative to traditional organic photoreceptors. This allows the present embodiments to extend the lifetime of the device.
U.S. patent Ser. No. 12/366,665 to McGuire et al., filed Feb. 6, 2009, and U.S. patent Ser. No. 12/366,680 to Skorokhod et al., filed Feb. 6, 2009, hereby incorporated by reference in their entirety, describe an apparatus for forming a latent image via scorotron charging coupled with TFT discharging or TFT photoreceptor addressing/discharging. However, these designs still require the use of charge carriers to selectively discharge the photoreceptor's surface to create the desired electrostatic image (i.e., the devices require the incorporation of charge transport compounds).
The present embodiments provide digitalization of the xerographic marking process in a manner that results in a smaller, smarter and more efficient machine.
Conventional photoreceptors are disclosed in the following patents, a number of which describe the presence of light scattering particles in the undercoat layers: Yu, U.S. Pat. No. 5,660,961; Yu, U.S. Pat. No. 5,215,839; and Katayama et al., U.S. Pat. No. 5,958,638. The term “photoreceptor” or “photoconductor” is generally used interchangeably with the terms “imaging member.” The term “electrophotographic” includes “electrophotographic” and “xerographic.” The terms “charge transport molecule” are generally used interchangeably with the terms “hole transport molecule” or “electron transport molecules.”